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CROR Engine debris Middle level Impact and Mechanical test

Periodic Reporting for period 2 - ELEMENT (CROR Engine debris Middle level Impact and Mechanical test)

Reporting period: 2018-03-01 to 2019-08-31

The European Union (EU) aeronautic industry is a world leader in its sector, and contributes to the EU economy with more than 500000 jobs and with a turnover of close to 140 B€. Regarding the production of civil aircraft, EU companies have, right now, about the 40% of the global market of short/medium range aircrafts. The objective of the Clean Sky 2 program is to build a platform to potentiate the innovation in this important industry for the EU.

Fuel consumption is probably the most important factor in the civil aircraft industry, and almost all the innovations are focused in this subject, always without compromising the security. Lower fuel consumption not only means lower operating cost of the airlines, but also lower CO2 emissions. The challenge proposed in this program is to address technologies that could allow achieving a 20% in specific fuel consumption; it is expected that these innovations could be introduced in the aircraft with market entry between 2025 and 2030.

One of the most promising technologies that could allow achieving the aforementioned goal is the Counter Rotatory Open Rotor (CROR) engine, which could offer an improvement in fuel consumption in the range of 15% - 20% compared to the actual engines. In order to use these new engines the aircraft structure should be tolerant to its failure. In particular, the topic of this project is focused in blade release or an Uncontained Engine Rotor Failure (UERF); under these circumstances high energy debris could impact to the fuselage, causing large structural damages that could compromise the aircraft structure safety. The current proposal is focused in the development and maturation of innovative shielding solutions to sustain high and low energy debris associated with the engine failure.

There are two overarching objectives in this project. The first one is to validate the maturity level of different technologies and structural solutions, to protect the rear-end structure from different impacts associated to engine failure. To this end both real and virtual impact tests of debris associated with the engine failure will be performed on both simple panels and full-scale representative aircraft structures.

The second objective of this project is to advance in the development of virtual testing methodologies. The economic impact of performing real experimental tests for the aircraft companies is very high, and virtual testing could diminish the number of experimental test (and hence its economic impact), which ideally could be limited to the ones that allow the aircraft certification. Right now the virtual testing technique is widely used in static problems, but its application under dynamic (impact for instance) conditions is limited. This project will allow improving the virtual testing for impact problems, increasing the competitiveness of the EU aircraft companies.
The main objective of this project is to validate the maturity level of different technologies and structural solutions, to protect the rear-end structure of a civil aircraft from different impacts associated to engine failure. The project defines two steps in approaching to this problem. The first one (level 1) considers small flat panels in order to compare different shielding solutions, whereas in the second one (level 2) full scale aircraft structures will be contemplated in order to validate the shielding solutions selected in level 1 phase. Up to now level 1 step has been concluded; the level 2 has been started and some experimental test has been performed up today.

The first part of the work has focused in preparing the experimental set-up for the experimental tests; this was a hard work since two different projectiles have been used (CFRP prism fragment and a steel sphere) and also different rig setup has been developed for monolithic, nets and dry fabrics shields. At the same time numerical simulations have been performed to analyse the best boundary conditions for the shielding considered. In the second period (from month 19th to month 36th) the L1 tests have been finalised, and the analysis of the tests have concluded the best shielding configurations in terms of weight. In this period also the level 2 tests have been defined and the experimental set-up has been developed and manufactured; in this second level the structures to be studied are representative of an aircraft, with curvature, stringers and frames.
The CROR engines seem to be the best option in order to increase the fuel efficiency and the economics of the commercial civil aircraft for low and medium range. The use of this engine presents many challenges to the engineers, because of its position in the rear-end, which will promote many modifications regarding the different systems. One of the main objectives of this project is to validate the maturity level of different shielding solutions to protect the rear-end against the impact of both blades and debris in case of engine rotor failure. Once validated, the path to adopt these new engines will be much clearer, since the protection of the fuselage is one of the key factors. It is possible to state then that the impact of the conclusions of this project will be very important and also will have important consequences on the rest of the program to adopt the CROR engines.

Another important objective of this project is to develop a virtual testing methodology to predict the behaviour of complex structures. Numerical models are usually validated with experiments performed on small specimens. Sometimes this validation could not be easily extrapolated to large structures such aeronautics ones; a representative aeronautic structure will include metallic frames, composite stringers and metallic joints between the different elements. In this project the numerical methodology will be validated with both simple specimens and complex structures (L1 and L2 tests). This tool will positively impact on the economics of the future developments for the TM, since the number of test for other high velocity impact analysis will be considerably reduced. These kinds of advances are key to increase the competitiveness of the European aeronautic sector.

The UC3M will dramatically increase its capacity of performing high velocity impact tests with the new launcher that will be one of the largest ones along Europe. This upgrade will help to increase the work load of the laboratory which, in the future, could allow the creation of a spin-off which will exploit the laboratory capacities and create new jobs. Spain has a very important unemployment problem, and the possibility to create highly skilled jobs is very important for the Spanish society.

Apart from the impact of achieving the two main objectives it is important to mention other potential spin-off impacts. One is for the Vázquez y Torres Ingeniería SL (VTI) company (one of the partners of this proposal), since the development of a large experimental device will add some skills to its capacities, which could later be used for other projects, increasing its portfolio of products. This company will increase its competitiveness in the field of experimental setup developing for the aeronautic and aerospace industries.
Square barrel developed to launch L2 metallic fragments
L2 structure to be tested